Study on instability mechanism and control technology of surrounding rock of crossing area in deep cross roadway

Aiming at the technical problems of poor bearing capacity of triangular coal pillar, high risk of surrounding rock instability and difficult maintenance of roadway in deep cross roadway, based on the engineering background of the inner section of the track crossheading in 150105 working face of a mine, this paper uses theoretical analysis, numerical simulation and field investigation to determine the stability of the triangular coal pillar based on the maximum inscribed circle diameter theory. The stress evolution characteristics of the triangular coal pillar under the influence of double mining and the deformation law of the surrounding rock of the roadway are analyzed, and the mechanism of the large deformation of the triangular coal pillar is revealed. The results show that the theoretical bearing strength of the triangular coal pillar in the crossing area is 27.29 MPa, the stability coefficient is 0.91, and the triangular coal pillar is in a metastable state after the roadway is excavated. Under the influence of single-sided mining stress, the bearing capacity decreases, and the peak stress on the side of the coal pillar shifts to the solid coal body. Under the influence of double mining, the instability and failure characteristics of the triangular coal pillar are significant. The application of support-unloading coupling control technology of “opposite tension anchor cable + grouting reinforcement + roof cutting and pressure relief” and the control technology of surrounding rock in cross triangle area are put forward. The practice results show that during the mining period of this working face, the maximum roof subsidence on the side of the coal pillar is 317 mm, and the maximum convergence of the coal pillar is 306 mm. No coal wall spalling and roof fall accidents are occurred, and the safe mining of the working face is realized. The combined support technology has obvious control effect on the surrounding rock in the triangle area.